The present invention relates to a new configuration for the dimples on a golf ball surface which improve the flight characteristics of the ball.
According to the United States Golf Association (U.S.G.A.) rules, a golf ball may not have a weight in excess of 1.620 ounces or a diameter smaller than 1.680 inches. The initial velocity of balls conforming to U.S.G.A. regulations may not exceed 250 feet per second with a maximum tolerance of 2%. Initial velocity is measured on a standard machine kept by the U.S.G.A. A projection on a wheel rotating at a defined speed hits the test ball, and the length of time it takes the ball to traverse a set distance after impact is measured. U.S.G.A. regulations also require that a ball not travel a distance greater than 280 yards when hit by the U.S.G.A. outdoor driving machine under specified conditions. In addition to this specification, there is a tolerance of plus 4% and a 2% tolerance for test error.
These specifications limit how far a struck golf ball will travel in several ways. Increasing the weight of a golf ball tends to increase the distance it will travel and lower the trajectory. A ball having greater momentum is better able to overcome drag. Reducing the diameter of the ball also has the effect of increasing the distance it will travel when hit. This is believed to occur primarily because a smaller ball has a smaller projected area and thus, a lower drag when traveling through the air. Increasing initial velocity increases the distance the ball will travel.
Drag on a golf ball is also reduced by forming a plurality of dimples, often circular, in the outer surface of the ball. The dimples serve to reduce the pressure differential between the front and rear of the ball as it travels through the air.
Various dimple configurations have been provided in order to improve the aerodynamic properties of a golf ball as it travels through the air. In the Sullivan U.S. patent application Ser. No. 09/259,673 there is disclosed a golf ball with contoured dimples, wherein a portion of a dimple is filled-in to provide a dimple of variable depth. In the Sullivan U.S. patent application Ser. No. 09/259,673, a golf ball having a plurality of dimples of different depth is disclosed. Groups of similar dimples are arranged within a geometric pattern on the ball, with the groups having increasing or decreasing depth. Both of the Sullivan inventions are commonly owned with the present invention.
The present invention was developed in order to provide a further dimple configuration wherein the dimples have a non-symmetric profile in order to improve the aerodynamic properties of a golf ball.
Accordingly, it is a primary object of the invention to provide a golf ball having a spherical surface which contains a plurality of dimples, each of the dimples having an outer edge at the intersection with the ball surface and a bottom surface defining a concavity. The bottom surface has a radius of curvature, and a portion of the bottom surface extends below the radius of curvature to define a nonsymmetric depth profile.
According to another object of the invention, the outer edge of the dimples has a circular configuration and the portion of the dimple extending below the radius of curvature is contained within one half of the dimple.
According to a further object of the invention, the dimples having a nonsymmetric depth profile are arranged in a geometric pattern on the surface of the golf ball.